Pattern regulation and growth control research with Drosophila melanogaster imaginal discs have focused attention at the cellular level by emphasizing the importance of local cell interactions. The general objective of the proposed research is to analyze in detail one aspect of cell-cell interactions in Drosophila imaginal discs, namely the size and distribution of gap junctions in wild-type and mutant wing discs. Computer-assisted image analysis and electron microscope sterielogical procedures will be used to derive a data-base of quantitative gap junction parameters from thin sections and freeze fracture replicas in mature wild-type wing discs for comparison with wing discs of different developmental stages and mutant phenotypes. Temperature-sensitive mutants will be used to determine if alterations in gap junctions precede, coincide with or follow the appearance of abnormal growth or abnormal pattern formation in the mutant wing discs. Neoplastic wing discs will be analyzed following serial subculture in adult abdomens to determine how gap junction size and distribution change with rapid growth. Cell interactions across membrane filters will be studied to assess the role of gap junctions in positional information and intercalary regeneration. The long-term objective of this research is to better understand the role of gap junctions in the establishment of patterns and in the control of growth in developing organisms.